The present invention relates to a heat-resistant aluminum-base composite and process of producing same, the composite being adapted for making components for internal combustion engines such as pistons, and more particularly to a heat-resistant aluminum-base composite containing evenly dispersed reinforcing particles in the aluminum matrix and process for making same.
It is generally known that components for internal combustion engines such as pistons are used under severe physical conditions such as at elevated temperatures as 150.degree. to 400.degree. C. To withstand the hard conditions the components are made of highly heat- and wear-resistant material which has good thermal conductivity and low coefficient of thermal expansion.
On the other hand, there is a strong demand for vehicles to be lightweight which requires individual components to be as light as possible. In addition, they must be easy to machine so as to increase the production efficiency and reduce the cost.
To satisfy such demands the components for internal combustion engines are made of Al--Si alloy made by an I/M method, such as AC8A and AC8B, but these materials are not sufficiently strong at elevated temperatures. For example, the tensile strength thereof is 17 kgf/mm.sup.2 at 200.degree. C., and 7 kgf/mm.sup.2 at 300.degree. C. As a result, it is difficult to make a thin and lightweight components with these materials.
To overcome the difficulty encountered by Al--Si alloy made by an I/M method, there is a proposal for using another type of Al--Si alloys made by a P/M method but they are costly and is not satisfactory in the heat-resistant property. There is another proposal for using aluminum alloys containing dispersed reinforcing particles of Al.sub.2 O.sub.3 and SiC in the aluminum matrix. It is found that this reinforced alloys increases the heat-resistant property but disadvantageously shortens the life of a cutting tool because of its excessive hard quality.